Inflammation results from a cascade of events that includes vasodilation accompanied by increased vascular permeability and exudation of fluid and plasma proteins. This disruption of vascular integrity precedes or coincides with an infiltration of inflammatory cells. Inflammatory mediators generated at the site of the initial lesion serve to recruit inflammatory cells to the site of injury. These mediators (chemokines such as IL-8, MCP-1, MIP-1, and RANTES, complement fragments and lipid mediators) have chemotactic activity for leukocytes and attract the inflammatory cells to the inflamed lesion. These chemotactic mediators which cause circulating leukocytes to localize at the site of inflammation require the cells to cross the vascular endothelium at a precise location. This leukocyte recruitment is accomplished by a process called cell adhesion.
Cell adhesion occurs through a coordinately regulated series of steps that allow the leukocytes to first adhere to a specific region of the vascular endothelium and then cross the endothelial barrier to migrate to the inflamed tissue (Springer, T. A., 1994, Traffic Signals for Lymphocyte Recirculation and Leukocyte Emigration: The Multistep Paradigm, Cell 76: 301-314; Lawrence, M. B., and Springer, T. A., 1991, Leukocytes' Roll on a Selectin at Physiologic Flow Rates: Distinction from and Prerequisite for Adhesion Through Integrins, Cell.65: 859-873; von Adrian, U., Chambers, J. D., McEnvoy, L. M., Bargatze, R. F., Arfos, K. E, and Butcher, E. C., 1991, Two-Step Model of Leukocyte-Endothelial Cell Interactions in Inflammation, Proc. Natl. Acad. Sci. USA 88: 7538-7542; and Ley, K., Gaehtgens, P., Fennie, C., Singer, M. S., Lasky, L. H. and Rosen, S. D., 1991, Lectin-Like Cell Adhesion Molecule 1 Mediates Rolling in Mesenteric Venules in vivo, Blood 77: 2553-2555). These steps are mediated by families of adhesion molecules such as integrin, Ig supergene family members, and selectins which are expressed on the surface of the circulating leukocytes and on the vascular endothelial cells. The first step consists of leukocyte rolling along the vascular endothelial cell lining in the region of inflammation. The rolling step is mediated by an interaction between leukocyte surface oligosacchamides (such as Sialylated Lewis-X antigen (Slex)) and a selectin molecule expressed on the surface of the endothelial cell in the region of inflammation. The selectin molecule is not normally expressed on the surface of endothelial cells but rather is induced by the action of inflammatory mediators such as TNF-.alpha. and interleukin-1. Rolling decreases the velocity of the circulating leukocyte in the region of inflammation and allows the cells to more firmly adhere to the endothelial cell. The firm adhesion is accomplished by the interaction of integrin molecules that are present on the surface of the rolling leukocytes and their counter-receptors-the Ig superfamily molecule-on the surface of the endothelial cell. The Ig superfamily molecules or CAMs (Cell Adhesion Molecules) are either not expressed or are expressed at low levels on normal vascular endothelial cells. The CAM's, like the selectins, are induced by the action of inflammatory mediators like TNF-alpha and IL-1. The final event in the adhesion process is the extravasation of the leukocyte through the endothelial cell barrier and the migration of the leukocyte along the chemotactic gradient to the site of inflammation. This transmigration is mediated by the conversion of the leukocyte integrin from a low avidity state to a high avidity state. The adhesion process relies on the induced expression of selectins and CAM's on the surface of vascular endothelial cells to mediate the rolling and firm adhesion of leukocytes to the vascular endothelium.
The induced expression of e-selectin and CAM's is mediated by the transcription factor NFkB. NFkB is a family of dimeric transcription factors made from monomers containing the 300 amino acid Rel domain. These factors can bind to DNA, interact with each other and bind to an inhibitor molecule termed IkB (Vermaa, I. M., Stevenson, J. K., Schwarz, E. M., Antwerp, D. V., and Miyamoto, S, 1995, Rel/NFlB/IkB Family: Intimate Tales of Association and Dissociation, Genes Dev. 9: 2723-2735; and Baldwin, A. S. 1996, The NFkB and IkB proteins: New Discoveries and Insights, Annu. Rev. Immunol. 14: 649-681). NFkB is found in the cytoplasm complexed with IkB. Activation of NFkB occurs in response to inflammatory mediators such as TNF-.alpha., IL-1, and lipopolysacchamide. Activation of NFkB requires phosphorylation of IkB followed by ubiquitinylation of the IkB molecule and subsequent degradation by proteosomes. Release of NFkB from association with IkB results in translocation of the dimer to the nucleus where it can associate with specific DNA sequences. The e-selectin gene and CAM's contain NFkB-recognition sequences upstream from their coding regions. The DNA-bound NFkB acting with other proteins in the transcription complex directs the expression of the e-selectin and CAM genes among others controlled by this transcription factor.
The present invention discloses compounds that inhibit the expression of e-selectin and ICAM-1 relative to VCAM-1. These compounds are useful for the treatment or prophylaxis of diseases caused by expression of adhesion molecules. These diseases include those in which leukocyte trafficking plays a role, notably acute and chronic inflammatory diseases, autoimmune diseases, tumor metastasis, allograft rejection, and reperfusion injury.